Armillaria mellea

The hall next to us cut a lot of elm trees down last year and used the cut trunks to make path markers, the ground is very very wet. This year every 'log' has sprouted the most amazing quantity of these, more than I've ever seen anywhere. Conservatively it could fill a skip.
Normally I'd just say honey fungus and take a pic, but I was bored.
So I've been trying to narrow it down more. I think there's a clear yellow tinge to the stem ring and the gills have gone dark brown on older ones. They also have a clearly dark centred concave cap when young.

Armillaria can spread exceptionally fast, and often mean death to host trees. The massed black mycelia spread underneath the bark of a tree until it seperates and the tree is lost, the mycelia then grows through the ground until it finds another host. 
Originally all 'honey fungus' were classified as the same, it's now widely accepted that this highly aggressive group of fungi has several distinct species. I think I've narrowed this down to mellia.